Compression therapy systems are used in several medical applications to apply rapid compressions to one or more appendages (e.g., arms, hands, legs, and feet) of a body. For example, compressions therapy systems are used to treat chronic wounds by applying pressure to an appendage having wounds to improve circulation around the wounds, or to improve blood circulation to treat angina or congestive heart failure (CHF), e.g., as in enhanced external counterpulsation (EECP) devices.
In some prior art compression therapy systems, a compressor may be utilized to compress air for storage into a storage tank. The stored air is then delivered from the storage tank to the inflatable compression device through a valve in rapid low pressure bursts to apply compression to the appendage. After each burst of air fills the inflatable device, another valve is opened on the release the air to the ambient conditions thereby removing compression from the appendage being treated. While such prior art systems may have had utility, the continuous need for significant amounts of air from the storage tank require the use of a relatively large compressor requiring significant amount of power and capital expense. Further, in some instances, it may be difficult for the compressor to keep up with the rapid cycling required of particular applications, and/or the valving used may not be precise enough to provide compression as precisely as desired.
Accordingly, some prior art similar systems have attempted to address some of these issues. For example, U.S. Pat. No. 6,984,215 to Shah (“Shah”) discloses a compression therapy system that utilizes a piston system and a supplementary bladder to overcome some of the aforementioned issues. In particular, instead of venting to the ambient air, the system disclosed in Shah utilizes a supplementary bladder and valve such that the air that would otherwise be vented and compensated for by the compressor of prior art systems is recycled by a bladder and forced back into the compression device by direct compression from a piston.
While the Shah disclosure represents an improvement over prior-art systems in efficiency and control, the direct use of a piston, operating directly on the compressed air in a supplementary bladder, is not as mechanically efficient as possible. Additionally, such a system may require complex and expensive piston position sensors in order to ensure that the use of the piston doesn't exceed the maximum pressure in the compression device, the potential failure of which could potentially result in significant patient injury. Accordingly, it would be desired to have a system and method for providing cyclic compression to a therapeutic device which is more efficient than prior art designs, does not require complex and expensive position sensors, and which provides a fail-safe for potential over-inflation of the compression device.